Piston structure



Oct. 8, 1935.

H. S. FRANK PISTON STRUCTURE Filed July 5, 1953 INVENTOR fiarzy ffiazakJzZ ISATTORNEY Patented Oct. 8, i935 UNITED sTATEs PATENT OFFICE Claims.

This invention relates to pistons in general, and particularly to apiston structure composed of two distinct parts made of metals havingdifferent coefiicients of expansion, such as described in my previousapplication for Letters Patent, Serial No. 638,686, filed October 20,1933, of which the present case is, in part, a division.

Pistons made of two metal parts are well known in the art. Yet, up tothe present time, it was pistons may be traced to the inefiicientconnections provided between the head and sleeve, in

that they do not allow for a necessary give of the less readilyexpanding piston part, the sleeve.

In the present case, the head portion of the piston is made of the usualdesign, but the connecting end of the sleeve, which is cast into thehead, is specially constructed so as to not only assure'a firm,permanent hold between head and sleeve, but at the same time, tofacilitate an unrestricted expansion of the head and of the connectingportion of the sleeve, without straining the latter in the least. Suchconnection may be best compared with an annular hinge construction or aniris diaphragm which automatically opens with the expansion of the headmaterial and closes when the latter contracts.

The object of the present case, therefore, is to provide a multiple partpiston, consisting of a head and a sleeve member, in which theconnection between the two members is so designed as to prevent themfrom coming apart, while at the same time permitting them tounrestrictedly expand or contract when subjected to variations oftemperature.

The foregoing and other objects of this invention will be more fullyapparent from the following description and the accompanying drawing,forming part of my disclosure, which drawing, however, is not intendedto limit me to the actual designs illustrated, and in which Figurelrepresents a cross-section through a portion of the connection betweenthe head and thesleeve of a piston.

Figure 2 is an elevation, partially in crosssection of the upper orconnecting end of a sleeve before having received its final form.

Figure 3 is a similar elevation of the sleeve with the connecting end inits final shape.

Figure 4 is a cross section through a part of 5 a modified form of ahead and sleeve connection.

Figure 5 is an elevation of a part of a sleeve with a modified form of aconnecting end.

Figure 6 is a top view thereof.

Figure '7 is a cross-sectional view similar to 10 that shown in Fig. 4,with the sleeve connection partially in elevation, and

Figures 8 to 12 illustrate still other modified forms of my head andsleeve connection.

Referring now to Figures 1 to 3, numeral I 0 15- denotes the head of apiston, made of cast metal, preferably aluminum or a compositionthereof, which possesses a higher coefficient of expansion than steel orcast iron. Numeral ll indicates a steel sleeve, the upper end of whichis specially prepared to serve as connecting portion and is cast intothe head material. This end portion of the sleeve, which is originallycylindrical (as seen in Fig. 2), is provided with a plurality oflongitudinal through-cuts l2, which are uniformly spaced over the entirecircumference of the sleeve. The metal above each cut is recessed as atI3. These recesses are of uniform width and are spaced by prongs ortangs I4, the width of which latter preferably equals that of therecesses.

Before casting the connecting end of the sleeve into the head material,the sections I5 of the sleeve, formed by cuts I 2 and recesses I 3, arebent inwards to form a frustum of a cone, as illustrated in Fig. 3. Itwill be observed that through this cone formation of the sleeveconnecting portion, the upper ends of cuts I2 and of recesses it becomenarrower, thereby producing dovetailed recesses, which are essential forthe purpose for which they are intended. The bending areas iii ofsection l5 substantially coincide with the bottom ends ll ofthrough-cuts l2, as is plainly visible from the cross-sected part ofFigs. 1 and 3. I

When the sleeve portion is thus prepared, it is cast into the headmaterial so that the dove-tail shaped recesses are completely covered.Due to the comparatively wide spaces provided between tangs Hi, themetal will readily fill recesses 56, thereby effecting a perfect unionbetween the two piston parts in that the head material will dovetailwith recesses l3. Through-cuts [2 being very fine, and in addition drawntogether at their top ends, will prevent the metal from-entering.

Consequently, the lower, wide areas of sections I5 r are left free forany subsequent movement induced by the expansion or contraction of thehead material. Such movement is facilitated through bending areas itwhich serve as fulcrums or hinges for sections IS.

The head material having a higher coefiicient of expansion than thesleeve will, when subjected to heat, expand more rapidly than thelatter. Since the head material is in interlocking engagement withrecesses l3 and tangs [4, it will force sections l5 radially outwards,which movement is aided both by the resiliency of the sleeve materialand the so-to-speak pivotal bending zones i5, provided for each section.During contraction of the head material sections l5 are caused to moveinwards.

In order to obviate any misunderstanding as to the movements of sectionsI5, it is to be noted that such movements are in reality infinitesimal.This is particularly due to the fact that during the casting operationthe heat of the molten head metal causes an appreciable expansion and anoutward movement of sections [5. As the head metal solidifies incooling, it shrinks and carries with it sections l5, drawing theminwards and bringing them under a slight tension, which facts becomebeneficial during the practical employment of the piston, when thelatter is subjected to quite a lesser heat than that employed in castingthe head material. The subsequent expansions of the head in an enginecylinder will, therefore, cause only relatively slight outward movementsof sections IS, without subjecting them to undue strains and stresseswhich might cause breakage at the hinge or bending areas I6. Similarly,when the head material contracts, sections l5 are brought back to theiroriginal position which they assume after the casting and coolingoperations.

In Figures 1 to 3 I have illustrated one of the many possible formsgiven to the connecting end of the sleeve. In Figures 4 and '7 amodified construction is shown, in which sleeve I8 is rolled at itsupper or engaging end to form annular grooves l9 and 2D. The rolledportion is slotted at 2| and is provided with either spaced recessessimilar to those explained in connection with Figures 2 and 3, or theconnecting end is sectioned off in the manner shown in Figures 5 and 6,where through-cuts 22 are illustrated, which terminate in V-shapedcontinuations 23, separating the attaching end of the sleeve intoindividual sections 24. The upper ends 25 of these sections are fullyembedded in the piston head material 26, while their next lower portions21 are embedded only up to their outer surfaces. The lowermost ends ofthe sections are free to move about annular bending line 28, when eitherexpanded or contracted by the variations of the volume of the headmaterial. In all other respects, the arrangement of this modification isthe same as described in connection with Figures 1 to 3.

In Figures 8 to 12 are illustrated still other possible constructions offlexibly connecting the head and sleeve members of a two-piece piston,by dividing or slotting the conically or otherwise inwardly directedattaching end of the sleeve into sections, the upper parts of which arealternately bent inwards and outwards. In Figures 8 and 9 the upper endof sleeve member is evenly slotted at 3B and formed into a cone. Aboutmidway between the bases of the slots and the ends of the tangs 3|,produced by the slotting operation, these tangs are alternately bentoutwards, as at 32, and left projecting inwards, as shown at 33. By thisarrangement the portions of the tangs above their middle form ananchorage for the sleeve within the head material, while their portionswhich are not absorbed by the 5 casting are free to fiex about bendingline 34.

Figures 10 and 11 illustrate a similar arrangement to that explainedabove, with the exception that sleeve 35 is bent in sharply at 36, andprongs 3'1 extend straight upwards until their upper ends 10 are bentalternately in outward and inward directions. These bent ends of theprongs are embedded in the casting of head 38. Figure 12 denotes amodified form of either of the constructions illustrated in Figures 9and 11, in that 5 prongs 39 are separated more generously at their top:by recesses 46.

All of the above described constructions have for their purpose toenable the connecting end of the sleeve or skirt to readily flex and toadjust 20 itself to the dimensional changes of the head, which changesare caused by the expansion and contraction of the head material, due tochanges in temperature, without unduly straining the sleeve material andwithout loosening the firm connection between the head and the sln rt.This is made possible through the particular crownresemblingconstructions of tangs, which are all separated from one another and arecapable of individually moving about their respective bending areas,which latter functions in the manner of hinges or fulcrums. Thedove-tail anchorage between the prongs and the head material provides afirm union between the two members, irrespective of their unequalexpansion, due to the diiferent coefiicients of expansion the materialsof the members may possess. Thus when the head (subjected to far greaterheat than the skirt and having a higher coefiicient of expansion) gainsin its dimension, the resilient individual prongs of the crown will moveoutwards, independently of any possible expansion of the sleevematerial, due to the influence of heat reaching it.

While I have illustrated a few modifications, it is quite selfevidentthat my invention may assume still other forms, as long as a trulyflexible connection between head and sleeve is produced. Consequently, Iherewith reserve for myself the right to make changes and improvementsin the construction of the piston, as may become advisable or necessaryin the course of producing it efiiciently on a large scale or otherwise,with the understanding that such innovations remain within the broadscope of my idea as covered by the annexed claims.

I claim:

1. A multiple-piece piston structure, comprising head and sleevemembers, the latter cast into the head material and provided with aconnecting end, consisting of a plurality of uniformly 0 arrangedprongs, finely spaced from one another at their lower ends, their upperends, separated by much larger spaces, being imbedded in the headmaterial, which latter fills these larger spaces, whereas the finelyspaced lower ends of the prongs are entirely free of the head material,said prongs thus being capable of individually adjusting themselves toany movement induced by the expansion or contraction of the headmaterial, without loosening their firm hold within the latter.

2. In a multiple-piece piston, the combination with a piston head, of apiston sleeve firmly connected therewith, the connecting end of thepiston provided with means for rendering the connection between the headand sleeve resilient and capable of expansion or contraction, induced bydimensional changes of the head material, said means consisting of aplurality of peripherally arranged prongs, separated at their bottoms byfine spaces, which are entirely free of the head material, andby largerspaces at their tops, which are entirely filled by the head material.

3. In a two-piece piston, the combination with a piston head, of apiston sleeve firmly but resiliently connected at one of its ends withsaid head, the connection between the two parts adapted to allow fordimensional changes of said head (due to temperature fluctuations)relative to said sleeve, without affecting the firmness of theconnectionwith said head, said connection consisting of an annular arrangement ofuniformly spaced prongs, arranged in off-set relation to the body of thesleeve, and separated at their lower ends by fine spaces which are freeof the head material, their upper ends being separated by relativelylarge spaces which are entirely filled by the head material.

4. A two-piece piston, comprising a head and a sleeve, the latter castat one of its ends into the head material, the cast-in sleeve-endprovided with means for interlocking with the head material and forallowing the latter to change its dimensions Without afiecting its firmconnection with said sleeve. said interlocking means consisting of anannularly arranged set of prongs, disposed angularly relative to thebody of the sleeve and separated at their lower ends by fine spaces,free of the head material, and at their upper ends by substantiallylarger spaces, said upper ends being imbedded, whereby the largerspaces, separating these upper ends, are completely filled with the headmaterial.

5. A two-piece piston, comprising a head and a being independent of theexpansion (due to heat) of the sleeve material, the sleeve end connectedwith the head material consisting of a conical arrangement of uniformlyspaced prongs, the lower ends of the prongs being separated by narrowcuts, the upper prong ends being spaced by large, substantiallydove-tailed cuts, said upper prong ends being completely imbedded in thehead material, so that the latter entirely fills the large cuts, whileleaving free the narrow cuts.

HARRY S. FRANK.

